PHP - 服务层类实例化导致无限循环

Question

我有执行业务逻辑的服务层类。

我有一个类说UserService，它执行与用户角色相关的服务，例如检查用户是否是管理员、用户是否有权访问项目、用户是否具有特定角色等。还有另一个类说ProjectService处理与项目相关的事情，例如获取项目成员、项目详细信息等。

UserService 
   $projectService;  //class variable

   hasProjectAccess(){
   {
     ...
     projectMember = projectService->getProjectMembers();
     ...
   }

   isUserAdmin(){
       return true|false; //just an example
   }

ProjectService 
   $userService;    //class variable
   getProjectMembers(){
   {
     ...
     perform some logic to create array of members
     ...
     if(userService.isUserAdmin())
        .. perform some other logic
     ...
   }

我使用的是 Slim 3，我使用它的 Container 类来实例化和注入所有依赖项。

现在，当我尝试实例化 UserService 类时，我必须在其中实例化 ProjectService 类（使用 setters 方法），而后者又必须实例化 UserService 类......等等......这会创建一个无限循环（循环依赖）。

我正在尝试在 Java/Spring 中实现类似的功能，您的类中有不同的服务，它们使用 Spring 连接到其中，因此您不必担心循环依赖。

除了基础之外，我对 PHP 不太熟悉。

如果需要更多信息，请告诉我。

Answer 1

Pimple 在 Slim3 中用作依赖容器，不如 Java f.ex 中的 Spring 强大。它只是一个简单的容器，只有基本的功能。

所以当只使用 pimple 函数时，您需要自己初始化具有循环依赖关系的对象：

class A {
    private $b;
    public function __construct(B $b) { $this->b = $b; }
}
class B {
    private $a;
    public function setA(A $a) { $this->a = $a; }
}

$container = new \Slim\Container;
$b = new B;
$a = new A($b);
$b->setA($a);

$container['A'] = function($c) use ($a) {
    return $a;
};
$container['B'] = function($c) use ($b) {
    return $b;
};
$aFromContainer = $container['A'];

我对 slim 容器进行了一些小改动，以便可以自动化这个过程（通过这项工作，我不知道它在大型项目中的效果如何）。

class MyContainer extends \Slim\Container 
        implements \Interop\Container\ContainerInterface {
    private $resolveStack = [];
    private $resolveLater = [];

    /**
     * @see \Pimple\Container::offsetSet()
     *
     * Additionally define objects which will be later set with a method.
     */
    public function resolveLater(string $id, callable $value, array $later) {
        $this[$id] = $value;
        foreach($later as $item) {
            if(!isset($this->resolveLater[$item])) $this->resolveLater[$item] = [];
            $this->resolveLater[$item][] = $id;
        }
    }

    /**
     * @see \Pimple\Container::offsetGet()
     *
     * Additionally set objects which were previously defined in #resolveLater.
     */
    public function offsetGet($id) {
        if(isset($this->resolveStack[$id])) { return $this->resolveStack[$id]; }
        $this->resolveStack[$id] = parent::offsetGet($id);
        if(isset($this->resolveLater[$id])) {
            foreach($this->resolveLater[$id] as $item) {
                $this[$item]->{'set' . $id}($this->resolveStack[$id]);
            }
        }
        return array_pop($this->resolveStack);
    }
}

以上示例：

class A {
    public function setB(B $b) { $this->b = $b; }
    public function setC(C $c) { $this->c = $c; }
}
class B {
    public function setA(A $a) { $this->a = $a; }
    public function setC(C $c) { $this->c = $c; }
}
class C {
    public function setA(A $a) { $this->a = $a; }
    public function setB(B $b) { $this->b = $b; }
}
$container = new MyContainer;
$container->resolveLater('A', function($container) {
    return new A;
}, ['B', 'C']);
$container->resolveLater('B', function($container) {
    return new B;
}, ['A', 'C']);
$container->resolveLater('C', function($container) {
    return new C;
}, ['A','B']);
$a = $container['C'];
var_dump($a);

这将输出如下内容：

object(C)[20]
  public 'b' =>
    object(B)[22]
      public 'a' =>
        object(A)[21]
          public 'b' =>
            &object(B)[22]
          public 'c' =>
            &object(C)[20]
      public 'c' =>
        &object(C)[20]
  public 'a' =>
    object(A)[21]
      public 'b' =>
        object(B)[22]
          public 'a' =>
            &object(A)[21]
          public 'c' =>
            &object(C)[20]
      public 'c' =>
        &object(C)[20]